Color television camera with dichroic mirrors

ABSTRACT

A color television camera having a photographic lens, dichroic mirror means for separating a light passing through said photographic lens into a plurality of chromatic rays and image pickup tubes for receiving said respective chromatic rays, said color television camera comprising means for deflecting in one plane a main light path which is not reflected by said dechroic mirror means and relay lens means having at least part thereof arranged adjacent said deflecting means, said dichroic mirror means inclusing at least two dichroic mirrors each arranged forwardly and rearwardly of said deflecting means and said relay lens means, one of said dichroic mirrors being positioned so as to lead one of said chromatic rays along a side light path parallel to said main light path and outside a plane in which said main light path lies, another one of said dichroic mirrors being positioned so as to lead another one of said chromatic rays along a side light path parallel to said main light path and lying in said plane, and the image-forming surfaces of said image pickup tubes being located substantially in the same plane.

08-01-72 XR 39681q521.

United States Patent [151 3,681,521 Doi et al. [451 Aug. 1, 1972 [54]COLOR TELEVISION CAMERA WITH DICHROIC MIRRORS [72] Inventors: YoshikazuDoi; Toshiro Kishikawa,

both of Ohmiya-shi; Hiroshi Nomura, Tokyo, all of Japan [73] Assignees:Fuji Shashin Kabushiki Kaisha, Oh-

miya-shi, Saitama-ken; Nippon Television Hosomo Kabushiki Kaisha, Tokyo,Japan [22] Filed: Jan. 21, 1969 21 Appl. No.: 792,264

[30] Foreign Application Priority Data Jan. 30, 1968 Japan ..43/5609[52] US. Cl. ..178/5.4 E, 350/171 [51] Int. Cl. ..H04n 9/08 [58] Fieldof Search ..350/169, 171, 172, 173; 352/41, 42, 66, 67; 178/5.4 E, 5.4TC

[56] References Cited UNITED STATES PATENTS 2,829,195 4/1958 Goldmark..l78/5.4 0 3,515,460 6/1970 Baluteau et al. ..178/5.4 0 3,521,9447/1970 Kishikawa .350/173 FOREIGN PATENTS OR APPLICATIONS 1,168,7634/1964 Germany ..178/5.4 TC

Primary Examiner-Robert L. Griffin Assistant Examiner-George G. StellarAttorney-Ralph E. Burcknam, Jesse D. Reingold, Robert R. Strack andHenry A. Marzullo, Jr.

[ 5 7] ABSTRACT A color television camera having a photographic lens,dichroic mirror means for separating a light passing through saidphotographic lens into a plurality of chromatic rays and image pickuptubes for receiving said respective chromatic rays, said colortelevision camera comprising means for deflecting in one plane a mainlight path which is not reflected by said dechroic mirror means andrelay lens means having at least part thereof arranged adjacent saiddeflecting means, said dichroic mirror means inclusing at least twodichroic mirrors each arranged forwardly and rearwardly of saiddeflecting means and said relay lens means, one of said dichroic mirrorsbeing positioned so as to lead one of said chromatic rays along a sidelight path parallel to said main light path and outside a plane in whichsaid main light path lies, another one of said dichroic mirrors beingpositioned so as to lead another one of said chromatic rays along a sidelight path parallel to said main light path and lying in said plane, andthe image-forming surfaces of said image pickup tubes being locatedsubstantially in the same plane.

3 Claims, 11 Drawing Figures PATENTEDMJB I I9 2 sum 1 or a FIG. PRIORART FIG 3 E M @Q. 2 i W (b M NU M W 6 PATENTEDAUB um 3.881.521

SHEET 3 BF 3 b (c) Me) COLOR TELEVISION CAMERA WITH DICHROIC MIRRORSBACKGROUND OF THE INVENTION The present invention relates to a colortelevision camera.

In a color television camera, a light passing through a photographiclens is generally separated into three colors by means of dichroicmirrors after passing through a relay lens and the rays of therespective colors are led into respective image pickup tubes.Conventional color television cameras have been bulky as a whole due tothe arrangement of the light paths extending from the photographic lensto the image pickup tubes, and therefore inconvenient in handling.

SUMMARY OF THE INVENTION The present invention contemplates theprovision of a color television camera which is small in size andcompact in form compared with the conventional color television cameras.

According to the invention, there is provided a color television camerahaving a photographic lens, dichroic mirror means for separating a lightpassing through said photographic lens into a plurality of chromaticrays and impage pickup tubes for receiving said respective chromaticrays, said color television camera comprising means for deflecting inone plane a main light path which is not reflected by said dichroicmirror means and relay lens means having at least part thereof arrangedadjacent said deflecting means, said dichroic mirror means including atleast two dichroic mirrors each arranged forwardly and rearwardly ofsaid deflecting means and said relay lens means, one of said dichroicmirrors being position so as to lead one of said chromatic rays along aside light path parallel to said main light path and outside a plane inwhich said main light path lies, another one of said dichroic mirrorsbeing positioned so as to lead another one of said chromatic rays alonga side light path parallel to said main light path and lying said plane,and image-forming surfaces of said image pickup tubes being locatedsubstantially in the same plane;

The main light path and the side light paths are preferably located soas to pass the respective apices of a regular polygon having a number ofsides equal to the number of these light paths. Namely, the light pathsare located so as to pass the apices of an equilateral trianglerespectively where a light passing through the photographic lens isseparated into three chromatic rays. According to the invention, a colortelevision camera can be constructed in very small size and compact formcompared with the conventional ones.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showingthe optical system of a conventional color television;

, FIG. 2 is a diagram showing an arrangement wherein the image-formingplanes of respective image pickup tubes are located in the same verticalplane;

FIG. 3 is a diagram showing the arrangement of FIG. 2 modified so as toobtain more bright images;

FIG. 4 is a diagram showing an arrangement wherein a main light path isdeflected;

FIG. 5 is a perspective view showing diagrammatically an embodiment ofthe image pickup tube arrangement according to the present invention;

FIGS. 6 and 7 are perspective views showing diagrammatically embodimentsof the optical system of this invention;

FIGS. 8 and 9 are front views showing other embodiments of the opticalsystem; and

FIGS. 10 and 11 are perspective views showing diagrammatically stillother embodiments of the optical system wherein four image pickup tubesare used.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 in which isshown the arrangement of the optical system employed in a conventionalcolor television, reference numeral 1 designates an image-forming planein which a field lens 10 is located, and reference numerals 2 and 3designate relay lenses between which a flux of light is usuallyparallel. Reference numerals 4 and 5 designate dichroic mirrors todecompose a light into three colors, 6 reflectors and 7 finalimage-forming planes, that is, the photoelectric surfaces of imagepickup tubes 8. The dichroic mirror 4 reflects only part of the light,e.g. blue color, thereon, while allowing the remaining part to passtherethrough, whereas the dichroic mirror 5 reflects only the other partof the light, e.g. red color, while allowing the remaining part, i.e.green color, to pass therethrough, whereby the light is separated intothree colors. In this case, the light path of a color which is notreflected on the dichroic mirrors 4, 5, i.e. the straight light pass inthe diagram, is referred to as main light path a, and the other twolight paths, i.e. the light paths of the colors reflected on thedichroic mirrors 4, 5, as side paths b and 0. According to thearrangement shown, the lengths of the light paths between the forwardrelay lens 2 and the respective backward relay lenses 3 along theoptical axes of said respective lenses are substantially the same and,therefore, the horizontal positions of the three image pickup tubes 8are largely staggered. Namely, the image-forming planes of the imagepickup tubes are not located in the same plane. FIG. 2 shows anarrangement in which the three image pickup tubes 8 are arranged in thesame positions horizontally so as to locate the image-forming planesthereof in the same plane. In this case, the distances between theforward relay lens 2 and the backward relay lenses 3 in the respectivelight paths are not equal to each other, so that it becomes necessary toeither make the flux of light between said lenses completely parallel ordifferentiate the focal distances of the relay lenses 3 in therespective light paths.

In addition, according to the arrangement shown in FIG. 2 it isdifficult to obtain a bright image on the image-forming plane or thephotoelectric surface 7 of each image pickup tube 8. This is because thelengths of the light paths between the forward relay lens 2 and thebackward relay lenses 3 located in the side light paths are so long thatcompensation of aberration becomes difficult and further the quantity ofperipheral light is reduced substantially. Alternatively, the forwardlens 2 may be eliminated and all lenses may be concentrated at thepositions of the backward relay lenses 3, but this method has thedisadvantage that the lenses used must be extremely large in diameterfor obtaining bright images, with the accompanying result that thelenses collide against each other.

Now, in order to locate the three image pickup tubes 8 in the samehorizontal positions and yet to obtain bright images, the arrangementshown in FIG. 3 may be considered. Namely, the lenses are segregatedinto forward relay lens 2 and backward relay lenses 3, and the dichroicmirrors 4, are located forwardly and rearwardly of the forward relaylens 2 respectively. This arrangement enables the distance between therelay lenses 2 and 3 to be much shortened compared with the arrangementof FIG. 2, as color separation is required only once between the relaylenses 2 and 3, and therefore advantageous from the standpoint ofcompensation of aberration as well as the quantity of peripheral light.It is of course possible to use lenses of complicate structure for thebackward relay lenses 3 for obtaining bright images. In the side lightpath b of the light which is reflected on the dichroic mirror 4, locatedforwardly of the forward'relay lens 2, are provided relay lenses 2 and3.

In the arrangement shown in FIGS. 1 to 3 inclusive, the main light patha is a straight line. Therefore, the distance from a lens 10 to theimage pickup tube 8 is considerably long, which gives a large influenceon the size of the entire camera. It will, therefore, be seen that thesize of the entire camera can be made small by deflecting the main lightpath a in an L-shape as shown in FIG. 4. In FIG. 4 (in which is shownthe main light path a only and the side light paths b, c are omitted),reference numeral 16 designates a photographic lens and 17 designates abeam-splitting film coated on the surface of a prism or mirror andadapted to separate the light into luminance channel x and chrominancechannel y. Reference numeral 18 designates the photoelectric surface ofan image pickup tube 19 in the luminance channel, on which thephotographic lens 16 directly forms an image. If a camera is desired inwhich the luminance channel x is not required but the chrominancechannel y only is desired, such camera can be obtained by forming atotal reflection film on the prism or mirror, instead of thebeam-splitting film 17, and eliminating the image pickup tube 19.

Reference numeral 21 designates an image-forming plane of thephotographic lens 16 conjugate with the image pickup tube 19 and a fieldlens is located in this position. The main light path a extends upwardlyfrom the beam-splitting film 17 and is reflected perpendicularlyrearwardly on a reflector 22. Obviously, the reflector 22 may bereplaced by a prism. A forward relay lens 23 is located adjacent thereflector 22 as close to said reflector as possible, and a relay lens 24and an image pickup tube 27 are positioned rearwardly of said forwardrelay lens. Dichroic mirrors 25, 26 to form respective side light pathsb, c are placed forwardly and rearwardly of the forward relay lens 23.In order to reduce the entire length of the camera by effectivelyutilizing the space, it is necessary to locate the dichroic mirror 25,not between the reflector 22 and the lens 23 but forwardly of thereflector 22. In other words, the dichroic mirrors 25, 26 should beplaced on both sides of a group consisting of the reflector 22 and theforward relay lens 23.

It is obvious that the entire size of a color television camera islargely influenced by the relative positions and figures of the threeimage pickup tubes in the chrominance channel y. Namely, the size of thecamera would become large if the three image pickup tubes are locatedremote from each other at random or with the axes thereof extending indifferent directions. The arrangement of FIG. 5 is believed to be one inwhich the three image pickup tubes are arranged most compactlyspacewise. In FIG. 5, as seen, the axes 30, 31 and 32 of the three imagepickup tubes 27 are parallel to each other and pass the apices of anequilateral or approximately equilateral triangle in a planeperpendicular thereto respectively. Furthermore, the photoelectricsurfaces of the respective image pickup tubes are substantially on thesame plane. Needless to say, the entire arrangement becomes more compactas the lengths of the sides of the triangular, that is, the distancebetween the axes of the image pickup tubes, becomes shorter. If it ispossible electrically to arrange the image pickup tubes 27 in the mannerdescribed for forming optical impages on the photoelectric surfaces ofthe respective tubes and shortening the entire length of the opticalsystem, a color television camera of extremely small size could beobtained.

It has already been described that the arrangements of FIGS. 3 and 4enable an optical system to be obtained which is short in its entirelength and capable of forming bright images. In order to take outfurther two side light paths b, c from the main light path a shown inFIG. 4 and also to form the final images on the photoelectric surfacesof the respective three image pickup tubes arranged triangularly asshown in FIG. 5, it is only necessary that at least one of the two sidelight paths b, 0, taken out from the dichroic mirrors 25, 26 in FIG. 4,is not included in a plane in which the L-shaped main light path a lies.Such an arrangement will be described practically with reference toFIGS. 6 and 7 hereunder:

In FIG. 6, similar numerals indicate similar parts to those shown inFIGS. 4 and 5, and furthermore the dichroic mirrors and the reflectorsare indicated by black dots at the deflection points of the respectivelight paths for the sake of simplicity. The main path a shown in FIG. 4passes, in FIG. 6, through the field lens 20, the reflector 22, theforward relay lens 23 and the backward relay lens 24, and reaches theimage pickup tube 27. The dichroic mirrors 25, 26 are located forwardlyand rearwardly of the forward relay lens 23 respectively. The side lightpath b reflecting on the dichroic mirror 25 passes through anotherreflector 33 and a relay lens 23', while the other side light path 0 isreflecting on the dichroic mirror 26. Then, the side light paths b, care deflected to be parallel to the main light path a upon reflecting onrespective reflectors 34, 35 and after passing through backward relaylenses 36, 37, enter the respective image pickup tubes 27 which arearranged in a triangular shape with the opposite ends thereof located onthe same planes respectively. Namely, according to this arrangement theside light path c lies in a plane including the main light path a butthe other wide light path b does not lie in said plane.

With the arrangement described above, the final images can be formed onthe photoelectric surfaces of the respective triangularly arranged imagepickup tubes 27 and these final images formed from the three light pathsare located in substantially the same positions horizontally as will beapparent from the fact that the arrangement of this optical system is amodification of that shown in FIG. 3. It is to be noted that the angledefined by a plane including the side light path b and the planeincluding the L-shaped main light path a can be changed freely by thelengths of the respective light paths and depending upon the space whichis available.

Final image-forming planes, similar to those in FIG. 6, may also beobtained by the arrangement shown in FIG. 7 in which the side light pathb, taken out from the dichroic mirror 25, is included in a plane inwhich the main light path a lies and the side light path 0, taken outfrom the dichroic mirror 26, is not included in said plane.

As will be clearly understood from the foregoing description, in orderto obtain bright optical images on the photoelectric surfaces of theimage pickup tubes 27, arranged in the way shown in FIG. 5, by anoptical system which is short in horizontal length, it is necessary todeflect the main light path a in an L-shape, to locate part of the relaylens system as close to the deflection point of said main light path aspossible and to locate the dichroic mirrors on both sides of the groupconsisting of the reflector and the lens, each forwardly and rearwardlyof said group, and further, it is necessary to locate at least one ofthe two side light paths b, c extending from the respective dichroicmirrors, outside of a plane in which the L-shaped main light path lies.

According to the arrangement described above, a proper optical systemcan be designed even whenthe distance between the axes of thet'riangularly arranged image pickup tubes is reduced considerably.Practically speaking, with 25 mm. vidicons arranged in such a compactform that the axes thereof define an equilateral triangle of 35 mm.side, an optical system can be obtained which is suitably used in asuper-miniature color television camera on the order of 160 mm. in theoverall longitudinal length comprising F2 lens as image-forming lens.

In the illustration of FIGS. 6 and 7, the light is reflected on thedichroic mirror at an angle of 90 to the direction of incidence. Inpractice, however, such a condition tends to result in the so-calledcolor shading which makes it impossible to obtain a satisfactorychromatic effect. It is for this reason that the color separation asshown in FIGS. 8 and 9 becomes necessary. Namely, FIG. 8 exemplifies amethod of minimizing the color shading by making the angle a, defined bythe incident light axis and the reflecting light axis, as small aspossible upon suitably changing the angle of inclination of a dichoricmirror 40. FIG. 9 exemplifies a method of making the angle a furthersmaller by changing the angle of inclination of a dichoric film 41 bymeans of prisms. These methods of color separation as shown in FIGS. 8and 9 can be incorporated in the optical system of this invention withno detrimental effect at all and will not make it difficult to practicethe present invention. It is also to be noted that a satisfactoryoptical system can he obtained according to the present invention byarranging more than three image pickup tubes in such a manner that thephotoelectric surfaces of the res ectivet bes arel ated int esa e la e athe axe thereo are parallel to earn-l otii er and de iiiie a polygon ina plane perpendicular thereto.

As an example, FIGS. 10 and 11 shows an optical system in which fourimage pickup tubes are arranged with the axes thereof defining a squarein a plane perpendicular thereto. As may be understood, the opticalsystem of FIG. 10 is a modification of FIG. 6 and the optical system ofFIG. 11 is a modification of FIG. 7. Descriptions on these opticalsystems are omitted by indicating similar parts by similar numerals andadditional side light paths by reference character b".

Weclaim:

1. A color television camera comprising a photographic lens throughwhich a main light beam passes, a first dichroic mirror means disposedafter said photographic lens for separating and reflecting a firstcomponent of the said main light beam while allowing the remaining partto pass therethrough and continue along a first portion of a main lightpath, deflecting means disposed after said first dichroic mirror meansin said first portion of said main light path and deflecting saidremaining part of said main light beam along a second portion of saidmain light path, said first and second portions of said main light pathbeing substantially perpendicular to one another and defining a firstplane, relay lens means disposed after said deflecting means in saidsecond portion of said main light path, second dichroic mirror meansdisposed after said relay lens means in said second portion of said mainlight path for separating and deflecting a second component of said mainlight beam while allowing the remaining part to pass therethrough alongsaid second portion of said main light path, a second deflector means,one of said first or second dichroic mirror means being arranged todeflect its component of said main light beam to said second deflectormeans so that the latter means deflects the last said component along alight path within the said first plane, a third deflector means, theother of said first or second dichroic mirror means being arranged todeflect its component of said main light beam to said third deflectormeans so that the latter means deflects the'last said component along aside light path located in a plane spaced from and parallel to saidfirst plane, and relay lens means followed by pick-up tube means forreceiving said remaining part of said main light beam and for receivingeach of said separated components, said image-forming surfaces of saidimage pick-up tube means being located substantially in the same plane.

2. A color television camera as defined in claim 1, in which said mainlight path and said light paths of said components are arranged so as topass the respective apices of a regular polygon having a number of sidesequal to the number of said light paths.

3. A color television camera as defined in claim 2 wherein said polygonis an equilateral triangle.

1. A color television camera comprising a photographic lens through which a main light beam passes, a first dichroic mirror means disposed after said photographic lens for separating and reflecting a first component of the said main light beam while allowing the remaining part to pass therethrough and continue along a first portion of a main light path, deflecting means disposed after said first dichroic mirror means in said first portion of said main light path and deflecting said remaining part of said main light beam along a second portion of saId main light path, said first and second portions of said main light path being substantially perpendicular to one another and defining a first plane, relay lens means disposed after said deflecting means in said second portion of said main light path, second dichroic mirror means disposed after said relay lens means in said second portion of said main light path for separating and deflecting a second component of said main light beam while allowing the remaining part to pass therethrough along said second portion of said main light path, a second deflector means, one of said first or second dichroic mirror means being arranged to deflect its component of said main light beam to said second deflector means so that the latter means deflects the last said component along a light path within the said first plane, a third deflector means, the other of said first or second dichroic mirror means being arranged to deflect its component of said main light beam to said third deflector means so that the latter means deflects the last said component along a side light path located in a plane spaced from and parallel to said first plane, and relay lens means followed by pick-up tube means for receiving said remaining part of said main light beam and for receiving each of said separated components, said image-forming surfaces of said image pick-up tube means being located substantially in the same plane.
 2. A color television camera as defined in claim 1, in which said main light path and said light paths of said components are arranged so as to pass the respective apices of a regular polygon having a number of sides equal to the number of said light paths.
 3. A color television camera as defined in claim 2 wherein said polygon is an equilateral triangle. 